i asked somewhere on our lists - does GStreamer utilize libalsa, which contains
a database of sound card features? I got no answer :-)
But it is my hypothesis, that sound is choppy, when frequency of sound stream
does not match some 'natural' freq. of sound card - and GStreamer does not do
any requantization. It is only a hypothesis.
Did You note some common conditions when sound is choppy and when it is not ?

(In reply to comment #3)
> Did You note some common conditions when sound is choppy and when it is not ?
It's always choppy when played via GStreamer from all apps using it, and it's
not choppy when a test .wav is played via aplay (which uses only alsa libs).
Also, when the GStreamer sound output is switched to OSS in the GNOME GStreamer
settings dialog, a test sound can be played OK. But Rhythmbox and Totem fail to
play via OSS, popping up an error.